I'm trying to make the open BHAV in the picture link to another BHAV. As you can see in the picture the other BHAV, 1052, is right there in the package but it still says unknown BHAV. How can I fix it?

You forgot the group. It matters. Also, if you're creating new BHAV in existing non-custom group, make sure there are no BHAVs in that group with the same instance that your new one. I usually leave good gap from the last used instance number to be on the safe side.